Rendering issue

Hello everybody!
My name is Gianni, I am from Italy and my professional activity Is sound and mastering audio engineering. I am pretty new on Resolve and use it for non-professional jobs like personal videoclip production etc...

I have always used the software for simple video editing, rendering the result once finished and never had any problem.
Yesterday and issue came in: after placing the job in the render queue I start the render of a project but the job stop always in the same point, at the 6%, and the whole computer stops working; just the mouse pointer moves but anything else respond so the only way is an hardware reset.
The most strange is that days ago I have already rendered the same project without problems, yesterday I have just changed a little and tried to render again and the issue appeared.

My current configuration is:
- Davinci Resolve 16
- Mac OSX High Sierra
- XFX RX 580 GPU
- I5 3GHz
- 32 Gb RAM DDR3 2400
- SSD 500Gb (system disk)
- Gigabyte Aorus Z370 Gaming 3
- External USB 3.0 drive: WD Red in RAID, this is the drive where the clips and database are located

Is there anything I can do to solve this?

Thank you much!